Play in tune and play in time.

When it comes to orchestral playing, musicians are consistently tested on these two abilities. When the aesthetics of the piece allow it, rubato, playing around with time, is acceptable if the conductor allows such a liberty. Orchestras are not democracies.

I can't think of a piece that exposes minute inaccuracies in these two faculties more than Joseph-Maurice Ravel'sBoléro, a popular work the Houston Symphony is performing this weekend.

Ravel composed Boléro as a ballet with allusions to the exotic Spanish slow-dance. Much to the surprise of the composer, the piece became his most famous composition. Due to its repetitive nature, Ravel thought orchestras would readily dismiss it for concert performance, that is, without dancers. He was wrong.

The art of perfecting challenging segments of orchestral repertoire is part of the rigorous training of all classical musicians. These excerpts are dissected, studied and polished as their accurate performance is the main determinant factor in winning a position in a symphony. We say winning because securing an orchestra job is like training and qualifying for the Olympics.

You advance from round to round showing off your skills, usually behind a screen, until a candidate is chosen — some orchestras have even gone through the whole process, often more than once, without finding a musician that's to their liking.

Boléro happens to be on the list of excerpts for almost all instruments, snare drum, saxophone, piccolo and English horn included. Young musicians often dismiss it as easy as the execution of the passage is not demanding, deceivingly.

But the extreme difficulty is realized in live performance. And here is why.

I describe the work as a 15-minute orgasm. It begins, almost from afar, with the unforgiving rhythm of the snare drum, setting up the unchanging tempo (speed), both in terms of the large beats and the division of such beats. The player then repeats it, without variation, through the whole duration of the piece. The focus required, of pseudo surgical intensity, is exhausting.

From then, a single theme is repeated, repeated and repeated, ad nauseam. The variations come as Ravel brilliantly explores orchestral color. That means different instruments showing off their different ranges in different combinations of increasing intensity, complexity and volume, until all has been explored and the piece comes to a raucous conclusion. That gives the piece its charm and interest. It has a sexy, almost naughty je ne sais quoi.

So, where does the difficulty come from?

Once the theme is exposed, initially by the principal flute, all instruments should match pitch, nuance, time, note length, phrasing and breathing. And given the idiosyncratic behavior of instruments — they are affected by temperature, humidity and just because — their individual tendencies have to be overcome to achieve perfection, like in a communist dictatorship.

Boléro is about playing in tune, playing in time and playing exactly like the person before you.

And how did the Houston Symphony do?

Percussionist Brian Del Signore's snare drum technique was flawless, achieving military perfection. Principal flutist Aralee Dorough's woody and sensual sound opened the work deliciously. But a couple of notes didn't speak, as the melody lies in the low register, the instrument's most unresponsive range. David Peck's clarinet playing was silky. But his length did not match Dorough's and was out of time with the unforgiving rhythm of the snare drum.

Adam Dinitz's English horn was downright perfect. The passage where the French horn, two piccolos (Allison Garza) and celeste (the instrument that is associated with the Sugar Plum Fairy movement of Tchaikovsky's Nutcraker) are playing the melody in different keys, a third apart, was magical — the stuff that fairy tales are made of, shimmering and crystal clear, perking me up and making anyone smile.

Hans Graf's tempo seemed just right. And the build up to the ecstatic culminating explosion made me want to smoke a cigarette afterwards.

But as a professional group, the Symphony has the ability and should perform to higher standards. Although the piece's popularity almost always encourages a standing ovation, I would encourage listeners to pay attention, listen critically and see whether the honor is well deserved.

Here is your challenge: Can you listen that attentively for 15 minutes or so, without loosing focus?

Also on this weekend's all Ravel program are his visually rich Rhapsodie Espagnole and L'Heure Espagnole (The Spanish Hour), a one-act operatic comedy rarely performed featuring mezzo-soprano Shepherd School of Music faculty Susanne Mentzer, student tenors Brenton Ryan and Rafael Moras, and baritones Samuel Schultz and Stephen Anthony Ray.

Houston Symphony's "Ravel's Spain with Bolero" plays at 8 p.m. Saturday and 2:30 p.m Sunday at Jones Hall.